This invention relates to novel cationic surfactants which are non-irritating to the eyes and therefore particularly useful in preparing new and improved hair conditioning preparations. These cationic surfactants may be used alone in certain hair conditioning preparations, e.g. creme rinses. They are also useful in other hair conditioning preparations, e.g. shampoos, based on anionic-cationic surfactant systems. In order to be highly useful in anionic-cationic surfactant systems in hair conditioning preparations the cationic surfactants must not only be non-irritating to the eyes but also compatible in adequate proportions with the anionic surfactant constituents without objectionably reducing the foam normally produced by the latter. Cationic surfactants do not as a class generally possess this particular combination of properties. For example, while the quarternary compound, stearyldimethylbenzylammonium chloride, has been used as a cationic surfactant in hair conditioning preparations, it is irritating to the eyes. Another cationic surfactant which is more closely related to the non-irritant sub-class thereof provided by and found useful in accordance with the present invention, but which exhibits excessive eye irritating properties, is stearylamidopropyldimethylamine lactate. The sub-class of cationic surfactants useful according to the present invention have the following general formula: ##STR3## wherein ##STR4## is a fatty acid group containing from 6 to 20 carbon atoms, and n.sub.1, n.sub.2 and n.sub.3 are the same or different integers not exceeding 3.
Accordingly, the object of the invention, generally stated, is the provision of cationic surfactants which are non-irritating to the eyes and, therefore, useful in hair conditioning preparations wherein they are compatible with other ingredients conventionally used in such preparations.
An important object of the invention is the provision of cationic surfactants which are particularly suitable for use as the cationic portion of anionic-cationic systems in hair conditioning preparations since these cationic surfactants are not only non-irritating to the eyes but also compatible with the anionic surfactant portion without adversely depressing foam formation.
Another important object of the invention is the provision of new and improved hair conditioning preparations based on anionic-cationic surfactant systems containing cationic surfactant portions provided by the invention.
The cationic surfactants of the present invention may be produced from available raw materials by known processes in known commercial equipment and may be readily incorporated in hair conditioning preparations in accordance with known formulating procedures and techniques. In such preparations the cationic surfactants of the present invention serve to improve the manageability of the hair, soften the hair and reduce static charges thereon, and facilitate and improve its combing properties. In the production of the useful cationic surfactants, the selected fatty acid and difunctional amine are condensed to the amido-amine which in turn is neutralized in aqueous solution with a selected acid having an innocuous anion. Useful fatty acids are those containing from 8 to 20 carbon atoms and are illustrated by caproic, caprylic, capric, lauric, myristic, palmitic, oleic, linoleic, stearic and isostearic acids. Commercial grades of these fatty acids may be used including mixtures thereof such as found in natural products, e.g. coconut fatty acids. While both saturated and olefinically unsaturated fatty acids may be used, the saturated acids are preferred for their excellent color and oxidative stability. The difunctional amines useful for condensation with the fatty acids include amines of the following structures: ##STR5## and in particular N-aminopropylmorpholine. The amido-amine condensation products are neutralized to form amine salts with either organic or inorganic acids. The useful acids, whether inorganic or organic must be characterized by an innocuous anion. The following lower molecular weight aliphatic carboxylic acids may be used: acetic, propionic, lactic, citric, tartaric, formic, dimethylolpropionic, ethylene diamine tetra acetic succinic, maleic and fumaric. Mineral or inorganic acids that may be used include: hydrochloric, nitric, sulphuric, and phosphoric acid. Other acids having innocuous anions that may be used include toluene sulfonic acid, dodecyl benzene sulfonic acid and benzoic acid.
For a more complete understanding of the nature and scope of the invention, reference may now be had to the following detailed description thereof wherein preferred working examples are set forth along with certain comparative test results.
Tests for compatibility, foam depression and eye irritation were made utilizing cationic surfactants of the sub-class or group provided by and found useful in accordance with the present invention, and for comparison, two cationic surfactants not found useful in accordance therewith. Two different types of anionic surfactants were also employed in conducting the tests. The cationic surfactants found useful in accordance with the present invention that were utilized in the tests were as follows: ##STR6##
The two cationic surfactants that were also used for comparison purposes, but not within the group of sub-class found useful in accordance with the present invention, were the following: ##STR7##
Stearylamidopropyldimethylamine Lactate (SDML). This compound is an eye irritant but otherwise useful in hair conditioning preparations. ##STR8##
Stearyldimethylbenzylammonium Chloride (SDBAC). This quarternary compound is an eye irritant and not adequately compatible in anionic-cationic surfactant systems.
The two anionic surfactants that were used in conducting the tests were:
Triethanolamine lauryl sulfate (TEALS)
Sodium lauryl ether sulfate (NaLES)